Abstract: A device for making a splice between optical fibers, has a hollow cylindrical elastomer member within a housing. The elastomer member seats in a V-groove and a screw is driven against the elastomer member to deform the member and so grip and render coaxial a pair of fibers having ends meeting within the elastomer member. Jacketed portions of the two fibers are clamped on each side of the junction zone.

Abstract: An optical cable is assembled by laying up optical fibres around the surface of a central strength filament. To minimize longitudinal tension in the fibres, air is directed along the surface of the cable in a feed direction. A blow-pipe type device has a pair of concentric tubes along the central longitudinal axis of which cable is drawn. The tubes are sealed together at the upstream end, the outer tube extending beyond the inner tube at the downstream end. Compressed air injected between the tubes is directed along the cable surface as it escapes from the downstream end. The air jet both frictionally urges fibres in the feed direction and creates a partial vacuum over the fibres to locally reduce contact pressure between the fibres and the central strength filament.

Abstract: An optical cable has a grooved central filament, the grooves following helical paths, the helices changing hand along the filament. In the manufacture of the filament, plastics is extruded past a fixed die and some way downstream, the filament is held and twisted first in one direction and then in the opposite direction so that the helical paths are introduced where the plastics exits the die. Dielectric optical waveguides are disposed in the grooves and the whole is surrounded by an extruded plastic sheath to produce an optical cable.

Abstract: An optical cable is assembled by inserting dielectric optical waveguides into periodically reversing helical grooves in the surface of a central filament. The invention is concerned with minimizing longitudinal tension in the waveguides. Powered rollers draw dielectric optical waveguide from fixed reels and delivers it, in a slack condition, to a guide unit which is mounted by means of a thrust bearing. The guide unit supports rods with apertures at their ends through which dielectric optical waveguide is guided, the rod ends being disposed within the grooves so that respective dielectric optical waveguides and grooves are maintained circumferentially coincident. Cable is drawn downstream of the guide unit to pull the filament and dielectric optical waveguides together at the guide unit and also to reciprocally drive the guide unit. As the filament, with dielectric optical waveguides positioned in its grooves, exits the guide unit, it is helically wound with tape.

Abstract: Low loss directional coupling of optical fibres is obtained by wrapping a tap fibre round a trunk fibre. Any cladding is first removed and then the tap fibre wrapped round the trunk fibre. The tap ratio can be varied by a variation in the number of turns or twists of the tap fibre around the trunk fibre. Signals can be abstracted by the tap fibre and also inserted.

Abstract: An optical cable is assembled by inserting dielectric optical waveguides into a filament having periodically reversing helical grooves. Dielectric optical waveguide is unwound from fixed reels by movement of the filament past the reels. A rotatable guide unit has flexible tubes through which dielectric optical waveguide is guided, the tube ends being disposed within the grooves so that respective dielectric optical waveguides and grooves are maintained circumferentially coincident.

Abstract: An optical fibre has a plurality of light conducting cores surrounded by a cladding layer of lower refractive index than the cores. A light conducting layer is on the cladding layer with a refractive index higher than that of the cladding layer, and a second cladding layer surrounds the light conducting layer and has a refractive index lower than that of the light conducting layer. Data signals can be propagated in the cores and a monitoring signal in the light conducting layer. Any attempt to tap the fibre to abstract data information results in aberration of the monitoring signal. Thus there is provided a secure optical fibre cable.

Abstract: An optical fibre is manufactured by forming a layer of fused silica, which may or may not be doped, on the inner wall of a fused silica tube by producing a plasma in the reactant gases flowing through the tube. By this means a higher temperature can be maintained inside the tube than at the tubes outer wall. The plasma is produced at substantially atmospheric pressure. Cooling gas is passed along the outer wall of the tube.